This invention relates to an improved seating assembly for use in vehicles such as trucks and buses.
The drivers of heavy vehicles who spend many hours in them need seating that is both comfortable and is an aid to safety. They need seating that can be adjusted to their own size and preferences and is adequately cushioned. Accordingly, many seating arrangements have been designed which enable fore-and-aft adjustability, which provide a suitable cushioning action to the seat, and which provide for adjustment of the back.
The present invention is an advance on these earlier inventions and relates particularly to a seat which is supported upon an air spring and in which compressed air is used to adjust the seat height.
It is very important that the adjustment of the seat height be coupled with an arrangement for maintaining the seat at the height to which it is set, even when the driver gets out of his seat or when he sits down rather heavily in it. Some seats are so made that when the driver begins to get out of the seat, the cushioning air forces the seat upwardly, making it difficult for the driver to get out and even more difficult for him to get back in. The present invention is directed to solution of this problem.
Another problem encountered with seats of this type and relatively unsolved, for little attention has been given to this problem, is that of response of the seat to pitch.
In a passenger automobile, the passengers are ideally located for riding comfort: low in the chassis and nearly midway between the axles. Vertical displacements of the wheels, due to bumps, tend to induce vertical displacements of the passengers, and no pitch component is introduced. In a large truck, however, and especially in a cab-over-engine type of vehicle, the occupant is located high above the axles in a cab that is supported on a rather narrow footing. As a result of this top-heavy arrangement, vertical displacements of the axles tend to induce horizontal displacements of the cab. In addition, the long frame rails of a truck deflect considerably under load. This up-and-down flexing of the frame rails provides one of the main vibratory inputs into the cab. As the rails flex, the front and rear of the cab move up and down unequally. Since the driver is situated above the cab mounts, he senses a fore-aft vibration.
The end result of all this is that the driver experiences a persistent "backslap" from the seat. This can be particularly bad even on apparently smooth roads such as freeways. The even spacing of dividers between concrete slabs will often cause this kind of vibratory response in a vehicle, because a resonance is created.
The present invention provides for the seat to move somewhat under either forward or backward pitch in order to stay with the driver better about a position to which the driver has set his normal position. However, as one leaves this centerpoint in either direction the movement of the seat is opposed more and more, so that there is a gradual but thorough snubbing of the pitch within a desired distance. This is an important feature in both driver comfort and safety.
The invention also provides for shock absorption and for the usual fore-and-aft adjustment of the seat.
One other problem to which the invention relates is that of providing rapid adjustment of the inclination of the seat back without requiring a more expensive type of seat back. This problem may be explained by noting that the back of the seat may be supported by rather lightweight sheet metal which is incapable of transmitting major forces. The inclination of the back should, however, be adjustable at one location, on either side of the seat, without having to adjust the two sides of the back separately, which would be extremely undesirable. The invention provides for this and does it with a novel structure having several advantages, which will be explained in the text.